1. Field of the Invention
The invention relates to video signal processing in general and more particularly, to video signal processing of repetitive scan data for centroid determination.
2. Description of the Prior Art
Processing of video signals resulting from a scanning process in order to locate a centroid representative of the "center of mass" of a target or target group, has been accomplished in various ways in prior art. Known methods and apparatus for performing this type of video processing, for example to generate missile tracking signals, involve either analog energy storage and comparison or digital processing and logic circuit comparison. Approaches to the general problem based on either of the foregoing generalizations have several inherent problems.
Systems involving analog energy storage are generally troubled by drift problems caused by temperature and/or operating supply potential variations. Also, the circuit parameters presented by various components in electrical circuits (e.g., resistors, capacitors, etc.), tend to change with age, thus requiring periodic recalibration. This is a particularly serious situation for items which must have a long shelf life and yet must operate properly when placed in service. In guided missile systems the overall instrumentation must be prepared to function at any time, without time allowance for calibration or checkout processes.
In respect to digital processing and logic comparison to provide the tracking signals, another set of problems accrue. Although digital processing can be made inherently free of drift problems which trouble the aforementioned analog systems, they tend to be more complex, require analog-to-digital converters, and are relatively expensive.
The manner in which the present invention deals with the shortcomings of the prior art by means of a novel approach to the problem, will be evident as this description proceeds.